1. Field of the Invention
The present invention relates to the art of determining a standard pulse-wave-propagation-velocity-related value for a living subject.
2. Related Art Statement
The pulse-wave-propagation-velocity-related information which is related to a velocity at which a pulse wave propagates in a living subject includes a pulse-wave propagation velocity, and a pulse-wave propagation time, for instance. A standard value of the pulse-wave-propagation-velocity-related information is obtained from a normal subject who is free from arteriosclerosis.
Arteriosclerosis is known as a factor that influences the pulse-wave-propagation-velocity-related information. This is utilized to evaluate a degree of arteriosclerosis of a living subject, i.e., the hardness of an artery of the subject. For instance, JP-A-9-122091 or its corresponding U.S. Pat. No. 5,743,856 discloses an apparatus for obtaining a pulse-wave propagation velocity to evaluate the hardness of the artery of the subject.
In a case where the obtained value of the pulse-wave-propagation-related information largely deviates from the standard value of the pulse-wave-propagation-velocity-related information, a medical treatment such as administration of drug is conducted on the subject or the subject is advised to change his/or her life habit in order to lower or reduce the degree of arteriosclerosis. Further, it can also be judged, from the pulse-wave-propagation-velocity-related value, to what extent the degree of arteriosclerosis is lowered owing to the administration of drug or the change of the life habit.
The standard pulse-wave-propagation-velocity-related value is not always constant, but varies depending upon blood pressure, age, etc., of a living subject. Therefore, it is not easy to determine the standard pulse-wave-propagation-velocity-related value. Further, it is not easy to judge to what extent the obtained pulse-wave-propagation-velocity-related value deviates from the standard pulse-wave-propagation-velocity-related value. In a case where the degree of arteriosclerosis is judged, the standard pulse-wave-propagation-velocity-related value determined in a present diagnosis tends to differ from that determined in a previous diagnosis conducted prior to the present diagnosis since the blood pressure measured in the present diagnosis is usually not the same as that measured in the previous diagnosis. Accordingly, it is difficult to judge whether or not the pulse-wave-propagation-velocity-related-value obtained in the present diagnosis deviates from the standard pulse-wave-propagation-velocity-related value, that is, whether or not the degree of arteriosclerosis is lowered.